LED (light-emitting diode) is a kind of p-n junction, which can emit spontaneous-emission light in regions of ultraviolet light, visible light or infrared light. LED light source refers to the light source which utilizes LED as the illuminant. With the development of LED light source, especially the development of the high-brightness LED light source, the packaging technology of LED light source becomes one of the research focuses.
The package for LED light source is an important part of a LED. Like the package for discrete semiconductor elements, it is required that the package of LED light source may prevent a LED chip from being effected by the external environment and may improve the abilities of heat dissipation and conduction. In addition to this, the package of LED light source has special natures. Differing from the package of discrete semiconductor element, the package of LED light source is required to improve light-emission efficiency, realize specific optics profile and output visible light, etc.
The conventional common package of LED light source includes lead package, surface mount package and chip on board (COB) package. In the COB package, a chip is integrated directly to a high thermal conductive material. Compared with the conventional package of LED light source, the COB package is characterized in that multiple LED chips may be packaged directly onto a printed circuit board with a metal or ceramic substrate, and the heat is dissipated directly via the printed circuit board, thereby not only simplifying the manufacturing process of frame and reducing the cost thereof, but also reducing effectively the thermal resistance of device. The LED light source with COB package has good heat dissipation performance and good cost performance, thus it has high market competitiveness.
For conventional COB packaging technology of LED light source, reference may be made to Chinese patent with publication No. CN103500787A published on Jan. 8, 2014. The package structure formed by means of the COB packaging technology is shown in FIG. 1, including: a substrate 100, where the substrate include an insulating ceramic substrate 101, a metal circuit layer 102 disposed on a first surface of the insulating ceramic substrate 101, and a metal film electroplated layer 103 disposed on a second surface of the insulating ceramic substrate 101, where the first surface is opposite to the second surface; LED chips 110 on a surface of the substrate 100; a dam 111 around the LED chips on the surface of the substrate 100; and a filling layer 112 filling the dam 111, where the filling layer 112 is doped with phosphors.
However, the package structure formed by means of the conventional COB packaging technology has poor uniformity of light-emission and high cost.